Former Malaysian premier Mahathir Mohamad is confident opposition parties can defeat Prime Minister Najib Razak in the country's next general election — an event that could see the 91-year-old return to power.

"If public opinion is to be taken into account, our chances are very good," he told CNBC in Tokyo, on the sidelines of the International Conference on the Future of Asia.

Speaking to a business forum at the conference, Mahathir also stated he was willing to temporarily step in as PM if there was no acceptable candidate following an opposition victory, according to Reuters. The next election has to be held by August 2018.

Malaysia's longest-serving prime minister, Mahathir launched the Malaysian United Indigenous Party (PPBM) earlier this year in the aim of overthrowing Najib, whose domestic and international standings have been hit amid his alleged role in a multi-billion dollar corruption scandal. Najib has denied the accusations.

Having unsuccessfully tried other means to topple Najib, including a vote of no-confidence and reporting the PM's misdeeds to the police, Mahathir told CNBC he was now depending on elections to achieve his goal.

"We find that (Najib's) policy is his tendency to borrow huge sums of money, which subsequently disappears and appears in his own account. I think this is very wrong indeed, and such a Prime Minister needs to be removed."

"Being aligned only to China would be the wrong thing to do ... Asian countries should really align themselves together so that they will form a good Asian bloc to protect their own interests. And that would include China and India."

During his 1981-2003 administration, Mahathir championed modernization by switching the country's manufacturing focus from resources to electronic equipment and cars, reflected by the establishment of car manufacturer Proton.

"I think for Proton's sake, that is the best thing that can happen. But we need to retain control over the car as it acts as a catalyst for the engineering industry," Mahathir told CNBC. "But of course, I think that given proper policies by the government, we need not sell the car (company) at all. We can turn it around fairly easily."

On the topic of President Donald Trump, the outspoken Mahathir said the U.S. leader was "doing the wrong things most of the time" and expected the Republican to "last only one term."

However, Trump's presidency has one key bright spot, Mahathir stated. "The U.S. has been following the same steps, the same attitude throughout their different presidents. It's about time somebody shocks them out of their complacency."

Washington must revise its approach to solving problems, not just via military means but through diplomacy as well, he continued. "I feel worried all the time with the U.S., whether it is Trump or somebody else because they have a tendency to resort to violence."